Methods, systems, and computer readable media for providing legacy devices access to a session initiation protocol (SIP) based network

ABSTRACT

Methods, systems, and computer readable media for providing legacy devices access to a session initiation protocol (SIP) based network are disclosed. One exemplary system comprises a session initiation protocol (SIP) based access proxy element communicatively coupled to a SIP based network that includes a registration engine configured to create a mapped entry in a database that associates an assigned SIP registration identifier to an identifier corresponding to a legacy endpoint device and configured to register the legacy endpoint device into the SIP based network using the assigned SIP registration identifier. The SIP based access proxy element further includes a session management module configured to establish a communications session involving the registered legacy endpoint device by interworking between a legacy control protocol and a SIP based call control protocol using the mapped entry in the database.

TECHNICAL FIELD

The subject matter described herein relates to legacy network equipmentand session initiation protocol (SIP) based networks. More specifically,the subject matter relates to methods, systems, and computer readablemedia for providing legacy devices access to a SIP based network.

BACKGROUND

At present, large service carriers are attempting to collapse fixedlegacy line communications networks into a session initiation protocol(SIP) based network, such as a common Internet protocol multimediasubsystem (IMS) core network. Notably, the service carriers believe acommon IMS core network will extend the reach of new multimediaservices, increase average revenue per user (ARPU), and reduce the totaloperating expenses (OPEX) associated with the public switched telephonenetwork (PSTN) core.

However, due to difficulties pertaining to the integration of IMScomponents with the current legacy access infrastructure, anyarchitecture plan that utilizes the associated legacy accessinfrastructure is a major deterrent to any IMS network consolidationplan. Although IMS is the preferred target architecture and continualreplacement of the current PSTN access infrastructure is noteconomically feasible, most service carriers want to ensure that anyinvestments made in telecommunications networks are IMS compatible butwithout completely abandoning the substantial PSTN architecture thatstill exists. Thus, integrating existing legacy copper lines into an IMScore network without modifying the physical access from these legacylines would be desirable.

A variety of PSTN emulation system (PES) solutions have been developedin an attempt to provide a solution to the aforementioned dilemma. Forexample, one such PES architecture proposed involves an IMS PESarchitecture that interworks H.248 gateways (typically as part of aMulti-Service Access Node (MSAN)) with the IMS core network by way of afunctional network element called the Access Gateway Control Function(AGCF). However, this IMS PES solution compels a network carrier to relyon an IMS Telephony Application Server (TAS) to provide fullytransparent voice over IP (VoIP) services. Similarly, this IMS PESarchitecture also introduces some problems with service behaviortransparency for the end users depending on the user equipment andsubscribed feature set. Namely, a network operator does not want tomodify a service set that can alter tariffs associated with end users orsubscribers. Services, such as access to 911, lawful intercept, supportfor coin pay phones, support for conventional POTS phones, and supportfor TTY phones, are provided in the PSTN. Thus, it would be beneficialto utilize a network element capable of providing legacy devices accessto an IMS core network without any modification to legacy access lineslocated within a traditional PSTN.

Accordingly, in light of these difficulties, a need exists for improvedmethods, systems, and computer readable media for providing legacydevices access to a SIP based network.

SUMMARY

Methods, systems, and computer readable media for providing legacydevices access to a session initiation protocol (SIP) based network aredisclosed. One exemplary system comprises a session initiation protocol(SIP) based access proxy element communicatively coupled to a SIP basednetwork that includes a registration engine configured to create amapped entry in a database that associates an assigned SIP registrationidentifier to an identifier corresponding to a legacy endpoint deviceand configured to register the legacy endpoint device into the SIP basednetwork using the assigned SIP registration identifier. The SIP basedaccess proxy element further includes a session management moduleconfigured to establish a communications session involving theregistered legacy endpoint device by interworking between a legacycontrol protocol and a SIP based call control protocol using the mappedentry in the database.

The subject matter described herein may be implemented in software, incombination with hardware or in combination with hardware and firmware.For example, the subject matter described herein may be implemented insoftware executed by a processor. In one exemplary implementation, thesubject matter described herein for providing legacy devices access to aSIP based network may be implemented using a non-transitory computerreadable medium to having stored thereon executable instructions thatwhen executed by the processor of a computer control the processor toperform steps. Exemplary non-transitory computer readable media suitablefor implementing the subject matter described herein include chip memorydevices or disk memory devices accessible by a processor, programmablelogic devices, and application specific integrated circuits. Inaddition, a computer readable medium that implements the subject matterdescribed herein may be located on a single computing platform or may bedistributed across plural computing platforms.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter described herein will now be explained with referenceto the accompanying drawings of which:

FIG. 1 is a flow chart illustrating a process for providing legacydevices access to a session initiation protocol (SIP) based network aredisclosed according to an embodiment of the subject matter describedherein

FIG. 2 is a block diagram illustrating a softswitch functioning as anIMS access proxy gateway according to an embodiment of the subjectmatter described herein;

FIG. 3 is a block diagram illustrating a proxy adjunct elementfunctioning as an IMS access proxy gateway according to an embodiment ofthe subject matter described herein; and

FIG. 4 is a block diagram illustrating a switchless proxy elementfunctioning as an IMS access proxy gateway according to an embodiment ofthe subject matter described herein.

DETAILED DESCRIPTION

The subject matter described herein includes methods, systems, andcomputer readable media for providing legacy devices access to a sessioninitiation protocol (SIP) based network. Although the followingdescription is made within the context of an Internet protocolmultimedia subsystem (IMS) network, any network utilizing a SIP basedInternet protocol (IP) solution for VoIP using an application server foraddressing legacy lines may be used without departing from the scope ofthe present subject matter.

In one embodiment, the present subject matter includes an Internetprotocol multimedia subsystem (IMS) access proxy element that allows forthe integration of legacy lines (e.g., copper telecommunication lines orhybrid fiber coaxial (HFC) cable) into an IMS core network. The IMSaccess proxy element may be used to receive lines originating fromlegacy devices via legacy peripheral devices, such as legacy switches(e.g., a TDM switch), line aggregation devices (e.g., a GR303 device orTR08 device), or any other aggregation and control device that supportsa legacy line.

The present subject matter allows for the evolution of an IMS corenetwork that incorporates at least a portion of the presently existingpublic switched telephone network (PSTN) architecture and utilizes thelegacy lines. The IMS access proxy element may be embodied as any one ofa plurality of deployment models, which may include 1) a softswitchintegrated model, 2) a legacy switch wrapper model (i.e., adjunct proxyelement), and 3) a switchless model.

The IMS access proxy element of the present subject matter may beembodied in such a manner that the proxy element appears as an “IMSagent” that is directly connected to an IMS core network. For example,the IMS access proxy element may be provisioned with a P-CSCF modulethat performs P-CSCF functions, such as facilitating registration andsupporting communications with the IMS core network. The IMS accessproxy element may also include a session management module (e.g., asyntax and semantics protocol module) that is responsible for mappinglegacy device protocols (which are used by the legacy devices) to SIP(e.g., a protocol which is used to communicate with the IMS core networkover an Mw interface).

FIG. 1 depicts a flowchart of an exemplary process that may conducted bya SIP based access proxy element (e.g., an IMS access proxy element),regardless of being embodied as a softswitch model, an adjunct proxyelement model, or a switchless model. In the following example, it isunderstood that the IMS access proxy element has established a networkconnection via a dedicated data connection (i.e., network attachment).

In block 102, mappings of legacy line identifiers and assigned SIPregistration identifiers, such as IMS identifiers, are created. In oneembodiment, the IMS access proxy element (e.g., a softswitch, a proxyadjunct element, a switchless element, etc.) may be connected to aplurality of PSTN peripheral devices, such as TDM switches and/orcopper-line aggregation devices (e.g., GR303 and TR08 devices). The PSTNperipheral devices serve to connect legacy endpoint devices to the IMSaccess proxy element. As described herein, a legacy endpoint device maybe defined as any user endpoint device that utilizes legacy copper wireor hybrid fiber-coaxial (HFC) cable to communicate media signals withina PSTN. For example, a legacy endpoint device may include a plain oldtelephone services (POTS) phone, a coin pay phone, an integratedservices digital network (ISDN) basic rate interface (BRI) device, aproprietary phone, or any phone that utilizes HFC or TDM/copper hostedlines. The IMS access proxy element may also be connected to a SIP-basedcore network, such as an IMS core network. In order to provide SIP-basedservice to the legacy endpoint devices, the IMS access proxy element maybe provisioned with a database that contains “assigned SIP registrationidentifiers” allocated by the service provider network (e.g., in oneembodiment, IP multimedia private identity identifiers (IMPIs)) that arerespectively mapped to an identifier associated with each of the legacyendpoint devices or legacy peripheral devices serviced by the IMS accessproxy element. For example, the IMS access proxy element may firstestablish the mapping state by utilizing an assigned SIP registrationidentifier that is typically created by the telephone company thatprovides service to the legacy device. The assigned SIP registrationidentifier may be a network identifier (e.g., allison.smith@telco.com)that may be used for others to contact the subscriber or used by thetelephone company for internal routing and control purposes. In someinstances, the network identifier may be a unique identifier such as aURL. The network identifier may be manually created and stored in theback office system with other subscriber profile information (e.g., adirectory number, a billing address, subscription details, location,etc.).

The IMS access proxy element may then link the assigned SIP registrationidentifier to a known legacy line identifier. An exemplary legacy lineidentifier may include a directory number, a subscriber phone number, ora line termination identifier (e.g., an identifier associated with anindividual line card identifier, a line group private identifier, a linetermination device identifier, or line termination port identifier)associated with one or more legacy devices. Legacy line identifiers arereadily assignable since the proxy element is attached/connected tolegacy endpoint devices or legacy peripheral devices (which subtend thelegacy endpoint device) via physical copper lines or HFC cable. Thismapping of the assigned SIP registration identifier and the legacy lineidentifier may be recorded in a local (or external) mapping databaseduring or after a successful IMS/SIP registration process.

In block 104, legacy devices are registered with the SIP based network,e.g., an IMS network, using the mapped subscriber identifiers. In oneembodiment, a proxy call session control function (P-CSCF) modulelocated on the IMS access proxy element directs a SIP REGISTER messageto an IMS core network over an Mw interface to register one or more ofthe legacy endpoint devices (i.e., the proxy element may register thelegacy endpoint devices in bulk or individually) serviced by the proxyelement. From the perspective of the IMS core network, the REGISTERmessage appears to be originated from an IMS agent. During the IMSregistration process, an IMS/SIP server (e.g., an S-CSCF server) in theIMS core network utilizes the assigned SIP registration identifier (orlegacy peripheral device identifier if registering in bulk) provided inthe REGISTER message to create a mapping to be used within the IMS corenetwork. For example, the IMS/SIP server may map the received assignedSIP registration identifier to a public subscriber profile associatedwith the registering legacy device. This mapping may be stored by theIMS/SIP server in a home subscriber server (HSS) element in the IMS corenetwork. After the mapping is performed and recorded in the HSS, anacknowledgement message may be transmitted to the IMS access proxyelement from the IMS network. For example, an S-CSCF server in the IMScore network may send a 200 OK acknowledgement message to a P-CSCFmodule in the proxy element indicating that the IMS registration processwas conducted successfully.

After the registration is established, the proxy element may also beconfigured to maintain the IMS registration for the legacy endpointdevices. For example, the IMS/SIP registration process establishes andmaintains a SIP registration session that allows SIP-based calls to bemade and received from legacy endpoint devices via the IMS access proxyelement. However, IMS/SIP registration sessions include built-in timeoutmechanisms which act as a security feature and terminate a SIPregistration session if no calls have been made during the predeterminedtimeout period. Accordingly, the proxy element may be configured toperiodically send IMS registration messages to the IMS core network tore-register the legacy device. By doing so, the proxy element maymaintain the SIP registration session (i.e., re-register prior to thetimeout period) so active calls handled by the proxy element are notterminated and/or new call attempts are not blocked or delayed. In block106, a communication is received from a legacy device. In oneembodiment, the IMS access proxy element may receive a call setuprequest from a legacy endpoint device directly or via a TDM switch orline aggregation device (depending on the embodiment type of the proxyelement).

In block 108, the communications session is maintained by interworkingbetween the SIP call control protocol and the legacy control protocol(e.g., a legacy line control protocol or legacy device controlprotocol). In one embodiment, the proxy element may then use the mappingof the legacy line identifier (associated with the calling legacy partydevice) to the assigned SIP registration identifier to forward a SIPINVITE message to the IMS core network. For example, the IMS accessproxy element may use the mapping to translate the appropriate legacycontrol protocol (e.g., a legacy line control protocol or legacy devicecontrol protocol) for the copper line endpoint to an IMS based SIP callcontrol protocol. Thus, the proxy element is able to send a SIP INVITEmessage in lieu of a PSTN-based call setup request because 1) the legacydevice has been previously registered with the IMS core network (seeblock 104) and 2) the proxy element can use the legacy lineidentifier-assigned SIP registration identifier mapping to convert orinterwork the PSTN message to a SIP based message. At this point intime, the IMS access proxy element handles/manages the communicationbetween the calling legacy endpoint device and the called party. Forexample, the IMS access proxy element may utilize the mapped databaseentry (i.e., the subscriber identifier-legacy device identifier mapping)to facilitate the call session involving the legacy device and the IMScore network. Similarly, the IMS access proxy element may also map anIMS based SIP call control protocol into an appropriate legacy controlprotocol used by the legacy device. As mentioned above, the IMS accessproxy element may be embodied in an existing softswitch, i.e., asoftswitch integrated model. FIG. 2 depicts an exemplary softswitch 204(or media gateway controller) that is communicatively coupled to an IMScore network 202 and capable of supporting copper line terminations to anumber of legacy endpoint devices, either directly or via legacyperipheral devices, as well as providing a variety of local servicecapabilities. Although FIG. 2 depicts an IMS core network 202, thesoftswitch may be utilized with any SIP based core network withoutdeviating from the present subject matter. In one embodiment, softswitch204 may be configured to support a plurality of legacy peripheral deviceinterfaces, such as interfaces associated with a line aggregation device(LAD) 206 (e.g., a TR08 or GR303 device). For example, LAD 206 may beconfigured to receive one or more connections from a plurality of legacyendpoint devices (LEDs) 208-210 (e.g., TDM phones, POTS phones, coinphones, etc.). Although FIG. 2 depicts softswitch 204 only supportingone line aggregation device and three legacy endpoint devices, anynumber of aggregation and endpoint devices may be supported withoutdeparting from the scope of the present subject matter. By supportingthe direct legacy line terminations (and the respective legacy deviceinterface protocols), softswitch 204 is able to act as a SIP proxy andconvert communications originating from the legacy line terminationsinto IMS communications to be received by IMS core network 202, and viceversa.

In one embodiment, softswitch 204 is configured to include a P-CSCFmodule 216, a registration engine 218, a local mapping database 220, asession management module 222, and a maintenance module 224. In oneembodiment, mapping database 220 may instead be a database that islocated external to softswitch 204. Mapping database 220 may be used tostore the mappings of legacy lines identifiers and assigned SIPregistration identifiers. P-CSCF module 216 may be configured tocommunicate with a CSCF element (e.g., an I-CSCF) in IMS core network202, and as such, enables softswitch 204 to appear as a P-CSCF residingin a foreign network to the IMS core network 202. Similarly, the use ofP-CSCF module 216 allows the legacy devices supported in the PSTN toappear as subtended IMS agents to the IMS core network 202.

Softswitch 204 may also include a registration engine 218 that works inconjunction with P-CSCF 216 to establish and maintain IMS communicationswith IMS core network 202. Notably, registration engine 218 may beconfigured to register all of the subscribers associated with the legacylines hosted by the legacy peripheral devices, maintain the IMSregistration state, and update the IMS registration state of any legacyline (e.g., when lines are placed in or out of service). In oneembodiment, P-CSCF 216 registers (either individually or as a group) allof the subscribers of the legacy lines hosted by the peripheral devicewith the IMS core network (e.g., via IMS registration).

For example, registration engine 218 may be configured to initiate andmanage the registration of a legacy device (which is unable to IMSregister) into IMS core network 202. Specifically, registration engine218 may be configured to issue a SIP REGISTER message (via P-CSCF module216) that is received by an I-CSCF in IMS core network 202. Once the SIPREGISTER message is received in IMS core network 202, the IMSregistration process is conducted normally within IMS core network 202.

Prior to or during the IMS registration process, registration engine 218may create a mapping relationship in database 220 between thenon-registering legacy device and a subscriber identifier. Normally, IMScore network 202 requires an IMS agent establishing or facilitating anIMS session to be identified with an IMS identifier (i.e., the assignedSIP registration identifier) such as a subscriber identity module (SIM)number, a packet cable device name, a GSM device name, a uniformresource identifier (URI), a uniform resource locator (URL), and thelike. However, legacy endpoint devices or line cards found in the PSTNtypically are not provisioned or associated with such identifiers.Therefore, registration engine 218 may be configured to assign anassigned SIP registration identifiers (e.g., obtained from the telephonecompany) to a legacy line on an individual or group basis. In oneembodiment, registration 218 may assign an assigned SIP registrationidentifier before the legacy endpoint device is brought into service(e.g., in the PSTN). Accordingly, registration engine 218 may beconfigured to register the legacy endpoint device into a SIP basednetwork before the legacy endpoint device is brought into service. Oncethe assigned SIP registration identifier is assigned to a legacy line,registration engine 218 records this legacy identifier-subscriberidentifier mapping in database 220. In one embodiment, an entry indatabase 220 may include a legacy identifier (e.g., a subscriberdirectory number (DN), a line termination identifier, a line cardidentifier, a line group identifier, etc.), that is mapped to thesubscriber identifier. More importantly, the legacyidentifier-subscriber identifier mapping enables softswitch 204 tofunction as a proxy to network 202 in order to manage a call sessionbetween IMS core network 202 and a legacy device in the PSTN.

In one embodiment, softswitch 204 may facilitate the call session bymapping SIP based call control protocols (e.g., IMS) into an appropriatelegacy control protocol (e.g., a legacy line control protocol or legacydevice control protocol) and/or vice versa. For example, sessionmanagement module 222 in softswitch 204 may be utilized to map IMS Mw(SIP) call control to a proprietary TDM device driving protocol (e.g.,GR303, TR08, NCS, and other proprietary protocols) to interface with theline cards that are supporting the legacy endpoint devices. Thus, byconverting a legacy call control protocol to a SIP call control protocol(and vice versa), softswitch 204 is able to present a legacy-based callto IMS core network 202 as a standard IMS call. For example, softswitch204 may map/convert a POTS offhook signal (and in some embodiments,digits) to a SIP INVITE message.

In one embodiment, registration engine 218 is also configured to manageand maintain the registration state of the legacy devices into IMS corenetwork 202. For example, registration engine 218 may be used tosimulate and manage SIP registration timeout periods andre-registrations.

In one embodiment, softswitch 204 also includes a maintenance module 224that performs all the maintenance activities associated with thesupported legacy lines. For example, maintenance module 224 may functionin cooperation with registration engine 218 to add, move, and changelines during maintenance periods. Notably; maintenance module 224 maycommunicate with registration engine 218 so that the registration stateof a line that is undergoing maintenance is updated (e.g., viare-registering and/or de-registering processes) with the IMS corenetwork 202.

In one embodiment, softswitch 204 is also modified such that all legacyline residential originations are routed to IMS core network 202 via aMw interface even if the terminating device is hosted by the samesoftswitch (i.e., the ½ call model). In this ½ model, softswitch 204 maybe configured with sufficient intelligence to leverage a full set oflocal features (e.g., call waiting, call forwarding, callpresentation/presentation restrictions, etc.) in order to ensure fullfeature transparency. This transparency may also include a number ofintelligent network (IN) originating and terminating triggers, as wellas a direct interconnection to fixed 911 services (as opposed toutilizing an emergency-CSCF).

In short, the softswitch integrated model configures or enables anexisting softswitch with the above-mentioned extensions to represent thelegacy devices (i.e., hosted copper end-users) as IMS subscribers into aSIP based network, such as IMS core network 202, while maintainingexisting legacy access equipment and feature transparency. Using IMScore network 202, a common translation/routing/interconnectinfrastructure can be supported in addition to advanced services, suchas Fixed Mobile Convergence (FMC), residential converged desktop, andthe like.

In another embodiment, the IMS access proxy element may be embodied as alegacy switch adjunct model. This deployment model may be used withlegacy switches (e.g., TDM switches) that cannot be upgraded orcollapsed to an existing softswitch (as previously depicted in FIG. 2).As shown in FIG. 3, a separate proxy adjunct element 304 may bepositioned between a TDM-based switch 306 and IMS core network 302.Although FIG. 3 depicts an IMS core network 302, the proxy adjunctelement may be utilized with any SIP based core network withoutdeviating from the present subject matter. Proxy adjunct element 304appears as a P-CSCF to IMS core network 302 as well as being configuredto support an ISUP interface or IN interface associated with aconnection from TDM switch 306. In one embodiment, proxy adjunct element304 is also responsible for performing the IMS registration of legacyendpoint devices that are communicatively coupled (either directly orvia legacy peripheral devices) to the TDM switch 306. Thus, the proxyadjunct element effectively represents the TDM switch into the IMS corenetwork 302. Although FIG. 3 depicts proxy adjunct element 304 connectedto only one TDM switch 306, additional TDM switches may be supportedwithout departing from the scope of the present subject matter.

In one embodiment, proxy adjunct element 304 is configured to include aP-CSCF module 316, registration engine 318, a local mapping database320, a session management module 322, and a maintenance module 324. Inone embodiment, database 320 may be a database located external to proxyadjunct element 304. Mapping database 320 may be used to store themappings of legacy lines identifiers and private network subscriberidentifiers. Registration engine 318 may be configured to function alongwith P-CSCF module 316 to establish and maintain IMS communications withIMS core network 302. Notably, registration engine 318 may be configuredto register the legacy lines connected to TDM switch 306, maintain theIMS registration state, and update the IMS registration state of anylegacy line. For example, registration engine 318 may be configured toinitiate and manage the registration of any one of legacy endpointdevices (LEDs) 310-315 into the IMS core network 302. Notably, proxyadjunct element 304 is capable of supporting a legacy endpoint devicedirectly connected to the interfaced TDM switch 306 or supporting alegacy endpoint device indirectly connected to TDM switch 306, such asvia a line aggregation device 308.

In one embodiment, registration engine 318 may create a mappingrelationship in database 320 between the TDM switch and an assigned SIPregistration identifier, such as an IMS identifier. For example,registration engine 318 may acquire an identifier for both the TDMswitch and a subtended legacy endpoint device (e.g., a directory number)which are then collectively mapped to a single assigned SIP registrationidentifier. Peripheral device identifiers and line card identifiers arenot necessary in this embodiment since these types of devices areincorporated within (i.e., are a part of) the TDM switch. Notably, theproxy element needs to know the identifier of the TDM switch hosting thelegacy endpoint device as well as the legacy endpoint device identifier.This combined legacy identifier-IMS identifier mapping enables proxyadjunct element 304 to function as a proxy for the TDM switch into theIMS core network. In one embodiment, registration engine 318 may performthe mapping process by creating an entry in database 320 by assigning anIMS identifier to the legacy line used by the TDM switch 306. Forexample, proxy adjunct element 304 may be configured to map a subscriberdirectory number with an IMS identifier that may later be used forregistration and initiation of an IMS call/session. In one embodiment,registration engine 318 may be configured to issue a SIP REGISTERmessage (via P-CSCF module 316) that is received by an I-CSCF in IMScore network 302. Once the SIP REGISTER message is received in IMS corenetwork 302, the IMS registration process is conducted normally withinIMS core network 302.

Proxy adjunct element 304 may act as a proxy to establish and manage acall session (e.g., a SIP registration session associated with settingup a call) involving a legacy endpoint device that is serviced by theIMS core network and TDM switch 306. In one embodiment, proxy adjunctelement 304 may establish and maintain the call session by mapping theIMS/SIP call control protocol into an appropriate legacy controlprotocol (e.g., a legacy line control protocol or legacy device controlprotocol) utilized by TDM switch 306 (and/or vice versa). For example,session management module 322 in proxy adjunct element 304 may beutilized to convert a SIP call control protocol into a TDM switchcontrol/interconnect protocol to interface with the legacy endpointdevices or the line cards that are supporting the legacy endpointdevices. In one embodiment, this may involve session management module322 converting the TDM communication protocols (such as ISUP, IN, PRI,H.323, etc.) to SIP. Thus, proxy adjunct element 304 is able to presenta legacy-based call session from TDM switch 306 into IMS core network302 as a standard IMS call.

In one embodiment, proxy adjunct element 304 may be configured totransmit PSTN signaling (e.g., ISUP signals) to IMS core network 302 byconverting PSTN signals to IMS SIP signals. The IMS SIP signals are thentransmitted by P-CSCF module 316 to the IMS core network 302 via an Mwinterface. In one embodiment, proxy adjunct element 304 may also convertbearer signals to RTP signals. Proxy adjunct element 304 may then sendthe RTP signals to IMS core network 302. Accordingly, proxy adjunctelement 304 may be communicatively coupled to a companion media gatewayfunction (not shown) for converting the bearer path from TDM to VoIP(e.g., RTP). The media gateway function may be embedded in proxy adjunctelement 304 or may reside in a separate element that is under thecontrol of proxy adjunct element 304.

As per the softswitch model, the local host switch may maintain a numberof local features for its hosted lines included local routing emergencyservices. Examples of local features include, but are not limited to,call waiting, call forwarding, call presentation/presentationrestrictions, and the like. If a policy interface is required, the proxyadjunct element 304 may support that as part of P-CSCF module 316.

In another embodiment, the IMS access proxy element may be embodied as aswitchless model which facilitates direct line card aggregation devicehosting. This is a further extension of the present subject matter wherethe local TDM switch intelligence is removed and a switchless proxyelement 404 illustrated in FIG. 4 directly interfaces with the lineaggregation device (LAD) nodes 410-414 via GR303, TR08, or proprietarytelecomm equipment manufacturer (TEM) interfaces. In one embodiment,switchless proxy element 404 performs basic call control functions byconverting line aggregation device protocols (e.g., TR08 and GR303protocols) into SIP. In one embodiment, switchless proxy element 404registers all the legacy endpoint devices into the IMS core network 402and provisions a database 420 in order to map the legacy endpointdevices with associated assigned SIP registration identifiers (e.g., IMSidentifiers). Switchless proxy element 404 is then able to maintain acommunication session by receiving communications from line aggregationdevices 410-414 and converting the communications from the proprietaryprotocols into SIP. The converted SIP communications are then forwardedto IMS core network 402. Thus, switchless proxy element 404 is able toproxy legacy copper lines in a manner where the legacy copper linesappear as IMS lines to IMS core network 402.

Feature control may be via the IMS TAS and the IMS core emergency callsupport would be leveraged. In this model, the switchless proxy element404 may also need to take on a maintenance control (aggregation elementmanager role) for line and node maintenance and test. In one embodiment,a maintenance module 424, such as a test head or the like, may beincluded in the proxy element.

In one embodiment, switchless proxy element 404 is configured to includea P-CSCF module 416, registration engine 418, a database 420, a sessionmanagement module 422, and a maintenance module 424. In one embodiment,database 420 may be database located external to switchless proxyelement 404. Registration engine 418 may be configured to function alongwith P-CSCF module 416 to establish and maintain IMS communications withIMS core network 402. Notably, registration engine 418 may be configuredto register the legacy lines connected to the line aggregation devices,maintain the IMS registration state, and update the IMS registrationstate of any legacy line. For example, registration engine 418 may beconfigured to initiate and manage the registration of any one of legacyendpoint devices (LEDs) 430-440 into IMS core network 420. Notably,switchless proxy element 404 is capable of supporting a legacy endpointdevice directly connected to one of the interfaced line aggregationdevices 410-414.

In one embodiment, registration engine 418 may be configured to issue aSIP REGISTER message (via P-CSCF module 416) that is subsequentlyreceived by an I-CSCF in IMS core network 402. Once the SIP REGISTERmessage is received in IMS core network 402, the IMS registrationprocess is conducted normally within IMS core network 402. As the IMSregistration process is conducted, registration engine 418 may create amapping relationship in database 420 between a non-registering legacydevice and an assigned SIP registration identifier (e.g., an IMSidentifier). Namely, the legacy identifier-assigned SIP registrationidentifier mapping enables switchless proxy element 404 to function as aproxy. In one embodiment, an entry in database 420 may include a linetermination identifier (e.g., an identifier of a line card in a lineaggregation device) that is mapped to an assigned SIP registrationidentifier.

During or prior to IMS registration being conducted (i.e.,acknowledged), registration engine 418 may perform the mapping processby creating an entry in database 420 by assigning an assigned SIPregistration identifier to the legacy line used by the line aggregationdevice. For example, switchless proxy element 404 may be configured tomap a line termination identifier (corresponding to the line aggregationdevice) with an IMS identification number for registration andinitiation of an IMS call/session. Namely, switchless proxy element 404may act as a proxy to manage a call session (i.e., register and maintainthe IMS session) between the IMS core network and a line aggregationdevice. In one embodiment, switchless proxy element 404 may maintain thecall session by mapping the call control from SIP into an appropriatelegacy control protocol (e.g., a legacy line control protocol or legacydevice control protocol) utilized by the line aggregation device (e.g.,TR08 or GR303). For example, session management module 422 in switchlessproxy element 404 may be utilized to convert SIP to a line aggregationdevice protocol to interface with the line cards that are supporting thelegacy endpoint devices.

In one embodiment, switchless proxy element 404 may be configured totransmit PSTN signaling (e.g., G303, TR08, H.323, and ISDN signals) toIMS core network 402 by converting the PSTN signals to IMS SIP signals.The IMS SIP signals are then transmitted by P-CSCF module 416 to the IMScore network 402 via an Mw interface.

In one embodiment, switchless proxy element 404 may also convert bearersignals to RTP signals. Switchless proxy element 404 may then send theRTP signals to IMS core network 402. Accordingly, switchless proxyelement 404 may be communicatively coupled to a companion media gatewayfunction (not shown) for converting the bearer path from TDM to VoIP(e.g., RTP). The media gateway function may be embedded in switchlessproxy element 404 or may reside in a separate element that is under thecontrol of switchless proxy element 404.

In conclusion, the IMS access proxy gateway bridges the gap between IMSand legacy lines for which there is no incentive to change or upgradethe copper line access (e.g., put in MSANs, cable, PON, etc.). Thepresent subject matter also permits a modest investment in softswitchesand packet line gateways (PLGs) for office collapse/consolidation arenot stranded and has a clear fit in future IMS core networks.

It will be understood that various details of the subject matterdescribed herein may be changed without departing from the scope of thesubject matter described herein. Furthermore, the foregoing descriptionis for the purpose of illustration only, and not for the purpose oflimitation, as the subject matter described herein is defined by theclaims as set forth hereinafter.

What is claimed is:
 1. A session initiation protocol (SIP)-based accessproxy device performing call session control functions, comprising: aprocessor; and a memory coupled to the processor, the memory havingprogram instructions stored thereon that, upon execution by theprocessor, cause the SIP-based access proxy device to: create a mappedentry in a database, wherein the entry associates a SIP registrationidentifier to a legacy identifier corresponding to a plain old telephoneservice (POTS) end-user communication device, wherein the POTS end-usercommunication device utilizes a legacy call control protocol; registerthe POTS end-user communication device into a SIP-based network usingthe associated SIP registration identifier, wherein a SIP registrationmessage includes the associated SIP registration identifier is sent to acall control function in an Internet protocol multimedia subsystem (IMS)core network; receive a communication session request from the POTSend-user communication device via the legacy call control protocol;establish the requested communication session on behalf of the POTSend-user communication device by converting between the legacy callcontrol protocol and a SIP-based call control protocol using the mappedentry in the database, wherein the legacy identifier of the POTSend-user communication device is provided only to the SIP-based accessproxy device; and perform call session control functions for therequested communication, wherein the legacy identifier of the POTSend-user communication device is provided only to the SIP-based accessproxy device.
 2. The SIP-based access proxy device of claim 1, whereinthe program instructions, upon execution by the processor, further causethe SIP-based access proxy device to add a line, move a line, or changea line associated with the POTS end-user communication device.
 3. TheSIP-based access proxy device of claim 1, wherein the POTS end-usercommunication device includes an endpoint device that is coupled to theSIP based access proxy device via one or more hosted copper lines orhybrid fiber-coaxial (HFC) cables.
 4. The SIP-based access proxy deviceof claim 3, wherein the POTS end-user communication device includes atleast one of: a coin pay phone or a POTS phone.
 5. The SIP-based accessproxy device of claim 1, wherein the legacy identifier corresponding tothe POTS end-user communication device includes a line terminationdevice identifier, a line termination port identifier, a directorynumber, or a subscriber phone number.
 6. The SIP-based access proxydevice of claim 1, wherein the associated SIP registration identifierincludes at least one of: a subscriber identity module (SIM) identifier,an Internet protocol multimedia subsystem (IMS)/global system for mobilecommunications (GSM) device name, an IMS/GSM packet cable device name, auniform resource indicator (URI), an Internet protocol multimediaprivate identity (IMPI), or a uniform resource locator (URL).
 7. TheSIP-based access proxy device of claim 1, wherein the SIP-based accessproxy device comprises at least one of a softswitch, a media gatewaycontroller, or a media gateway.
 8. The SIP-based access proxy device ofclaim 1, wherein the SIP-based access proxy device is interfaced with atime division multiplexing (TDM) switch, and wherein the programinstructions, upon execution by the processor, further cause theSIP-based access proxy device to associate the associated SIPregistration identifier with a TDM switch identifier.
 9. The SIP-basedaccess proxy device of claim 1, wherein the SIP-based access proxydevice directly interfaces with one or more line aggregation devices.10. A method, comprising: at a Session Initiation Protocol (SIP) basedaccess proxy device performing call session control functions andcommunicatively coupled to a SIP-based network: creating a mapped entryin a database, wherein the entry associates a SIP registrationidentifier to a legacy identifier corresponding to a plain old telephoneservice (POTS) end-user communication device, wherein the POTS end-usercommunication device utilizes a legacy call control protocol;registering the POTS end-user communication device into a SIP-basednetwork using the associated SIP registration identifier, wherein a SIPregistration message includes the associated SIP registration identifieris sent to a call control function in an Internet protocol multimediasubsystem (IMS) core network; receiving a communication session requestfrom the POTS end-user communication device via the legacy call controlprotocol; establishing the requested communication session on behalf ofthe POTS end-user communication device by converting between the legacycall control protocol and a SIP-based call control protocol using themapped entry in the database, wherein the legacy identifier of the POTSend-user communication device is provided only to the SIP-based accessproxy device; and perform call session control functions for therequested communication, wherein the legacy identifier of the POTSend-user communication device is provided only to the SIP-based accessproxy device.
 11. The method of claim 10, further comprising maintainingthe registration of the POTS end-user communication device in an event alegacy line associated with the POTS end-user communication device isadded, moved, or changed.
 12. The method of claim 10, wherein the POTSend-user communication device includes an endpoint device that iscoupled to the SIP-based access proxy device via one or more hostedcopper lines or hybrid fiber-coaxial (HFC) cables.
 13. The method ofclaim 12, wherein the POTS end-user communication device includes atleast one of: a coin pay phone or a POTS phone.
 14. The method of claim10, wherein the legacy identifier corresponding to the POTS end-usercommunication device includes a line termination device identifier, aline termination port identifier, a directory number, or a subscriberphone number.
 15. The method of claim 10, wherein the associated SIPregistration identifier includes at least one of: a subscriber identitymodule (SIM) identifier, an Internet protocol multimedia subsystem(IMS)/global system for mobile communications (GSM) device name, anIMS/GSM packet cable device name, a uniform resource indicator (URI), anInternet protocol multimedia private identity (IMPI), or a uniformresource locator (URL).
 16. The method of claim 10, wherein theSIP-based access proxy device comprises at least one of: a softswitch, amedia gateway controller, or a media gateway.
 17. The method of claim10, wherein the SIP-based access proxy device comprises a proxy adjunctelement that is interfaced with a time division multiplexing (TDM)switch, and wherein the method further includes associating theassociated SIP registration identifier with a TDM switch identifier. 18.The method of claim 10, wherein the SIP-based access proxy devicecomprises a switchless proxy element that directly interfaces with oneor more line aggregation devices.
 19. A memory storage device havingexecutable instructions stored thereon that, upon execution by aprocessor of a computer configured as a Session Initiation Protocol(SIP) based access proxy device, causes the computer to: create a mappedentry in a database, wherein the entry associates a Session InitiationProtocol (SIP) registration identifier to a legacy identifiercorresponding to a plain old telephone service (POTS) end-usercommunication device, wherein the POTS end-user communication deviceutilizes a legacy call control protocol; register the POTS end-usercommunication device into a SIP-based network using the associated SIPregistration identifier, wherein a SIP registration message includes theassociated SIP registration identifier is sent to a call controlfunction in an Internet protocol multimedia subsystem (IMS) corenetwork; receive a communication session request from the POTS end-usercommunication device via the legacy call control protocol; establish therequested communication session on behalf of the POTS end-usercommunication device by converting between the legacy control protocoland a SIP-based call control protocol using the mapped entry in thedatabase, wherein the legacy identifier of the POTS end-usercommunication device is provided only to the SIP-based access proxydevice; and perform call session control functions for the requestedcommunication, wherein the legacy identifier of the POTS end-usercommunication device is provided only to the SIP-based access proxydevice.